Porous fluorinated polymer materials that have numerous fine pores have been known for sometime. Further, the formation of a metal film through chemical plating (nonelectrolytic plating) on the surface inside the pores in these materials is also known, as shown in Japanese patent publication 60-500905, and U.S. Pat. Nos. 3,235,473 (LeDuc), 3,383,247 (Adlhart, et al), 4,204,918 and 4,348,429 (McIntyre, et al), 4,557,957 and 4,720,400 (Manniso).
According to this known technology, materials with a metal film on the surfaces inside the resin pores are manufactured through a series of steps in which first a porous fluorinated resin material is immersed in a water-soluble surfactant solution to fill the voids in the pores of the resin with the surfactant solution. Then a step is carried out in which the surfactant solution contained in the pores is replaced with an aqueous solution of a palladium/tin activator so that palladium is deposited onto the surface inside the pores. Then the solution inside these pores is replaced with hydrochloric acid, the hydrochloric acid inside these pores is replaced with a wash bath, and finally the material that has been thus treated is immersed in a chemical plating bath and subjected to chemical plating.
In this conventional method, when the material is taken out after being immersed in the water-soluble surfactant solution, there is a great decrease in the hydrophilicity of the inside surfaces of the pores, and when the inside surfaces of the pores are dried, these pore surfaces become water repellant, thereby making it difficult to fill the pores with the aqueous solution used in the next step. Consequently, with this conventional method, the aqueous solution contained in the pores must be subjected to a liquid-liquid replacement with the aqueous solution used in the following step in order to prevent the drying of the inside surfaces of the pores and fill the pores with the aqueous solution.
However, such methods involving numerous liquid-liquid replacement operations require precise control over the time, temperature, and pressure in order to accomplish the liquid-liquid replacement, and the inconvenience of these operations is a major drawback.
The present invention solves the above problems evident in the prior art by providing a method for efficiently forming a metal film on the surface inside of the pores in a porous fluorinated polymer material, as well as the porous fluorinated polymer outside surfaces with a metal film that is obtained with this method.